1. Field of the Invention
The present invention relates to a valve freeze control apparatus that limits malfunction of a valve, such as a throttle valve of an internal combustion engine, caused by water that is attached to the valve and that is then frozen. Also, the present invention relates to a sensor element breakage control apparatus that limits the breakage of a sensor element for sensing a specific component concentration in exhaust gas from breaking due to the water that attaches the sensor element.
2. Description of Related Art
During an excessively-low-temperature operational state, where an outside temperature drops below freezing, condensed water attached to a valve (for example, a throttle valve) mounted in an intake passage or an exhaust passage may be frozen even while the internal combustion engine is operated. Then, a rotational shaft portion of the valve may be frozen, and thereby the rotation of the valve may be disabled disadvantageously.
As a countermeasure for the above disadvantage caused by the freeze, JP-A-2002-161758 describes an art that vibrates the throttle valve in order to limit the freeze of the valve when it is determined that a condensed water generation condition is satisfied. For example, the above condensed water generation condition includes that the outside temperature is equal to or lower than a predetermined temperature.
Also, there is a case, where the internal combustion engine includes an exhaust gas sensor device that has a sensor element and an electric heater. The sensor element detects an O2 concentration and an NOx concentration in exhaust gas, and the electric heater heats the sensor element to activate the sensor element. In the above the internal combustion engine, when the electric heater is operated to heat the sensor element while condensed water is attached to the sensor element, the water-attached part of the sensor element may locally have a lower temperature compared with the other part of the sensor element. As a result, the above local cooling may cause thermal strain of the sensor element, and thereby the sensor element may break disadvantageously.
As a countermeasure against the above disadvantage caused by the attached water. JP-A-2004-69644 corresponding to US2004/0026408) describes that during a period, in which a condensed water generation condition is satisfied, the energization to the electric heater is prohibited such that breakage of the sensor element is limited. The above condensed water generation condition may be that temperature in the exhaust pipe is equal to or lower than a predetermined temperature.
Recently, alcohol-gasoline mixture and alcohol fuel are proposed as alternative fuel for the internal combustion engine. In the above, the alcohol-gasoline mixture has alcohol, such as methanol, ethanol, mixed with gasoline, and the alcohol fuel is made based only on alcohol. In the present specification, the above alcohol-gasoline mixture and the above alcohol fuel are indicated as alcohol blended fuel. The above disadvantages for the gasoline may occur when the alcohol blended fuel is supplied for combustion of the internal combustion engine.